Timing circuit for opening fuel injection valves

ABSTRACT

A fuel-injection arrangement for internal combustion engines with electromagnetically actuated fuel-injection valves and intake manifold. A monostable multivibrator provides output pulses having a duration dependent on at least one operating parameter of the engine, such as the suction pressure within the manifold behind the throttle valve. A pulse-extending stage connected to the monostable multivibrator emits an extending pulse adjoining each pulse from the multivibrator and having a duration which depends on the duration of the preceding pulse from the multivibrator. A second monostable multivibrator has an unstable state duration beginning with the extending pulse and lasting for a fraction of the duration of the extending pulse. A compensating network connected to the pulse-extending stage influences the duration of the extending pulse by either increasing or decreasing the duration of the extending pulse.

United States Patent 1 Dautel TIMING CIRCUIT FOR OPENING FUEL-INJECTIONVALVES [75] Inventor: Wolfgang Dautel, Esslingen,

[21] Appl. No.: 168,137

[30] Foreign Application Priority Data Aug. 8, 1970 Germany P 20 39486.9

[52] U.S. CL... 123/32 EA, 123/119 R, 123/140 MP [51] Int. Cl. F02115/00 [58] Field of Search 123/32 R, 32 EA,

123/32 AE,119 R [56] References Cited I UNITED STATES PATENTS 3/19705/1961 Zechnall et a1 133 32 EA lnoue 123/119 R June 26, 1973 PrimaryExaminer-Laurence M. Goodridge AttorneyMichael S. Striker [5 7] ABSTRACTA fuel-injection arrangement for internal combustion engines withelectromagnetically actuated fuelinjection valves and intake manifold. Amonostable multivibrator provides output pulses having a durationdependent on at least one operating parameter of the engine, such as thesuction pressure within the manifold behind the throttle valve. Apulse-extending stage connected to the monostable multivibrator emits anextending pulse adjoining each pulse from the multivibrator and having aduration which depends on the duration of the preceding pulse from themultivibrator. A second monostable multivibrator has an unstable stateduration beginning with the extending pulse and lasting for a fractionof the duration of the extending pulse. A compensating network connectedto the pulseextending stage influences the duration of the extendingpulse by either increasing or decreasing the duration of the extendingpulse.

8 Claims, 2 Drawing Figures 26 52 77 as "2 i TIMING CIRCUIT FOR OPENINGFUEL-INJECTION VALVES BACKGROUND OF THE INVENTION The present inventionrelates to a fuel-injection arrangement for an internal combustionengine which is equipped in particular with intake manifold injection. Acontrol arrangement determines the opening duration of at least oneelectromagnetically actuated fuelinjection valve. This controlarrangement is preferably constructed of a monostable multivibratorhaving output pulses with duration made dependent on at least oneoperating parameter of the engine. Such a parameter is preferably thesuction pressure within the intake manifold prevailing behing thethrottle valve. An electronic pulse-extending stage is connected to themonostable multivibrator and provides an output pulse adjoining thepulse emitted by the multivibrator. The duration of the pulse from thepulse extender is dependent upon the duration of the output pulse fromthe monostable multivibrator immediately beforehand. A second monostablemultivibrator whichis connected to the first multivibrator has anunstable state which be gins with the pulse from the extending stage andhas a duration which is a fraction of the pulse from the extended stage.

In fuel-injection arrangements of the above species, the quantity offuel injected can be made particularly precise in relation to the speedand load of the engine, for every suction cycle in a cylinder of theengine. This has the advantage above all that injurious exhaust gasesfrom the engine may be held at a minimum. In order to fit the openingduration of the injection valves to the prevailing operating condition,the fuel-injection arrangements known in the art use different deviceswhich provide the required electrical information as a function of theoperating conditions, for the control purposes. These devices, however,cannot be massfabricated while maintaining the required narrowtolerances at economical costs. The present. invention, therefore, hasas its basic object to provide an arrangement through which thetolerances of the individual devices as well as the tolerances of theengine are compensated through a correcting or compensation controldevice. This correction is superimposed so that-the magnitude of theopening duration is either shortened or extended and remains constantover the entire speed range. This is made so that too large an influenceis avoided at high speeds or high suction pressure. To provide thedesired correction, an adjustable voltage divider is provided inconjunction with the fuelinjection arrangement. This adjustable voltagedivider SUMMARYv OF THE INVENTION A fuel-injection arrangement used forinternal combustion engines provided with intake suction manifold andelectromagnetically actuated injection valves. A first monostablemultivibrator provides output pulses having a duration made dependent onat least one operating parameter of the engine, such as the suctionpressure within the intake manifold behind the throttle valve. Apulse-stretching or extending stage is connected to the first monostablemultivibrator and emits an extending pulse adjoining immediately thepulse from the first monostable multivibrator. The duration of theextending pulse is made dependent upon the preceding output pulse fromthe first monostable multivibrator. A second monostable multivibrator isconnected to the first monostable multivibrator and has an unstablestate duration which begins with the extending pulse and lasts for afraction of the duration of this extending pulse. A compensating networkis connected to the first monostable multivibrator and thepulseextending stage for influencing the duration of the extendingpulse.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an electrical circuit diagramof the fuelinjection arrangement for an internal combustion engine, inaccordance with the present invention;

FIG. 2 is a pulse-timing diagram of pulses prevailing in the circuitshown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, andin particular to FIG. 1, the fuel-injection arrangement shown therein isintended for operating a four-cylinder internal combustion engine 11.The sparkplugs 12 of this engine are connected to a high-voltageignition arrangement, not

shown. An electromagnetically actuated injection valve 14 is providedfor each cylinder branch leading from the intake manifold 13. Thesevalves 14 are located directly in proximity of the individual cylindersof the internal combustion engine, and in particular in proximity to theinlet valves, not shown. Fuel from a distributor 16'is transmitted toeach injection valve through a fuel line 15. The fuel pressure withinthe distributor l6 and the fuel lines 15 is maintained at approximately3 atm. through means of an electrically motor-driven pump 17 and apressure regulator 18.

Each injection valve 14 possesses an electromagnetic coil, not shown.One end of each coil is connected to ground potential, whereas the otherend of each coil is connected through one of the interconnecting lines19, with one of the four resistors 20. In the embodiment shown, allinjection valves are simultaneously operated in synchronous mannerrelative to the crankshaft rotations of the engine to actuate them totheir open positions. This occurs through the application of anelectrical opening pulse 1,. The duration of this pulse determines theduration of the fuel injection period. The power stage 22 is used foractuating the injection valves, and is described in further detailbelow.

The electronic control arrangement controls as'an essential part, amonostable multivibrator 25, an inverting stage 26, a pulse-extendingstage 27 connected to the stage 26, and an OR gate 28 to which the powerstage 22 is connected. A correction circuit or compensation circuit 30is, furthermore, provided.

The monostable means 25, have a multivibrator includes an inputtransistor 31 and an output transistor 32 having its base connected tothe collector of the transistor 31. From the collector of the outputtransistor 32, leads a series circuit to the positivesupply line 33,through a primary winding 35 of a transformer 36, and a resistor 34. Thetransformer 36 has an adjustable core- 37. The core 37 of thistransformer is mechanically'coupled, through linkage 38, with themembrane (not shown) of a pressure sensor 39. This pressure sensor 39 isconnected to the intake manifold 13 of the engine, and is located afterthe throttle valve 41 which is actuated by the accelerator, when viewedin the direction of intake in the manifold 13.

The input transistor 31 of the multivibrator 35 is maintained conductingin its inoperative state, through a resistor 43 which is connectedbetween the base of I this transistor and the positive supply line 33. Adiode 44 is, furthermore, connected between the base of transistor 31and the primarywinding 35 of the transformer 36. The other terminal ofthis primary winding of the transformer is connected to the junction oftwo resistom 46 and 47 which serve as a voltage divider.

The crankshaft 50 of the engineis coupled to a triggering means cam51-comprising a which actuates a switching arm 53 connected to thenegative voltage supply line 52 of a power supply not further shown. Theactuation of the switching arm 53 produces pulses J, for switching themultivibrator 25 to its unstable state, in a synchronous manner relativeto the crankshaft rotations. A charging resistor 55 is connected to thefixed contact 54 associated with the switching arm 53, and

one electrode ofa coupling capacitor 56 is connected to the junction ofthe terminal 54 and the resistor 55. The other electrode of thiscapacitor 56 leads to the negative voltage supply line 52 through aresistor 57. At the same time, a diode 58 is connectedbetween the baseof transistor 31 and the junction of the capacitor 56 and resistor 57.As long as the switching arm 53 is in the open position shown in FIG. 1,the capacitor 56 can chargethrough the two resistors 55 and 57 andacquire the voltage determined from that prevailing across voltagesupply ines 52 and 33. When the switching arm 53 is actuated by the'cam51 so that it becomes pressed against contact 54, the positively chargedelectrode of the capacitor 56 becomes connected with negative potential.As aresult, the base of the input transistor 31 strongly acquiresnegative potential so that the transistor 31 becomes turned off and theoutput transistor 32 becomes turned on.

The collector current of the output transistor 32 which flows throughthe primary winding 35, induces a voltage within the secondary winding45, so that the input transistor 31 is further held turned off. Theduration of the time during which the transistor 31 is thus turned off,is thereby determined by the pressure prevailing within the intakemanifold 13 of the engine. When this pressure drops considerably belowthe outer atmospheric pressure when the throttle valve 41 is eitherclosed or almost closed, then the pressure sensor 39 lifts the core 37in the direction of the arrow in the drawing, and increases thereby theair gap in the transformer 36. The inductance of the primary winding 35is thereby considerably decreased. In view of such decreased inducedvoltage, the input transistor 31 then turns rapidly to its initialconducting state, and the output transistor 32 becomes turned off anew.The pulse 1,, appearing at the collector of the output transistor 32has, thereby, a short duration of approximately 1.2 msec.

When, however, the accelerator or gas pedal 40 is depressed and thethrottle valve 41 is thereby moved into its open position, the airpressure behind the throttle valve is only slightly below that of theouter atmospheric air, even when the speed of the engine issubstantially high. Since under these circumstances the core 37 can onlybe lifted slightly, the primary winding 35 has a substantially highinductance, and this leads to a slow rise of the collector current inthe primary winding 35. The pulse J has an accompanying larger pulseduration, thereby, of approximately 4.2 msec.

In the embodiment shown, the pulse J,, is taken from the inverting stage26 of the output transistor 32, and is applied to the pulse-stretchingor extending stage 27. This stage 27 produces directly an extended pulseJ, connected to the pulse J,,. The duration of the pulse J, is largerthan the duration of thepulse J by an adjustable factor. This factor canbe made dependent on different operating conditions of the engine, asshown in the art. Such operating conditions of the engine can be, forexample, the cooling water temperature.

in particular, the pulse stretcher 27 contains a storage capacitor 60, acharging transistor 61, a discharging resistance ineans have in form ofa transistor 62, and a switching transistor 63 which has its. emitterdirectly connected to the minus voltage supply line 52. The base of thistransistor is .connected through a resistor 64 to this minus voltagesupply line, and at the same time, to one electrode of the capacitor 60,through a diode 83. The collector of the switching transistor 63 isconnected with its base to the collector of the transistor 62, throughthe diode 83. The base of the discharge transistor 62, on the otherhand, is connected to the junction of two resistors 65 and 66 forming avoltage divider. The emitter of transistor 62 leads 'to the posi tivesupply line 33 through a resistor 67. 1 t

The collector of the charging transistor 61 is connected'to the otherelectrode of the storing capacitor 60. This transistor is connected asan emitter follower, since its emitter leads to the positive supply line33 through the resistor 69, and its base is directly connected to thecollector of the inverting'transistor 70 of the inverting stage 26. Aresistor 73 is connected between the collector of the transistor 70 andthe positive supply line 33. A resistor 71, furthermore, is connectedbetween the base of transistor 70 and the voltage supply line 52. Aresistor 72 is connected between the collector of the output transistor32 and the base of transistor 70.

The collector of the transistor 70 leads to the base of transistor 75,through a resistor 76. The transistor 75 belongs to an OR gate 28. Aresistor 77 is connected between the base of the transistor 75 and thenegative supply line 52. A coupling resistor 78 is, furthermore,connected between the base of this transistor 75 and the collector ofthe transistor 63. A resistor 68 is connected between the junction ofresistor 78 and the collector of transistor 63, and the positive supplyline 33. The collector of transistor 75 leads to the positive supplyline 33 through a resistor 79, whereas a resistor 80 is connectedbetween the emitter of transistor 75 and the negative supply line 52.The base of a transistor 81 is directly coupled to the emitter oftransistor 75. This transistor 81 is of the npn type, and forms a powerstage 22 together with the pnp power transistor 80.

The principle of the circuit described thus far is known in the art. Theoperation of this circuit can, therefore, be described as follows: Whenthe engine operates the switching arm 53 and closes it through the cam51 during each rotation of the crankshaft, the input transistor 31becomes turned off, and the pulse J,, is generated in the mannerdescribed above. The duration of this pulse depends upon the rotationalspeed of the engine and the throttle valve position. During the intervalor duration of this pulse, the transistor 70 of the AND gate 26 isturned off, so that the transistor 75 belonging to the OR gate 28becomes conducting through the first coupling resistor 76. As a result,the transistor 81 and the power transistor 82 are also turned on. In theinitial state or inthe inoperative state, the collector potential of thecharging transistor 61, as well as the collector potential of theconducting inverting transistor 70 are substantially at the potential ofthe negative supply line 52. The voltage U across the storage capacitor60 is then substantially zero. As soon as a pulse 1,, begins, however,the base potential of the charging transistor 61 acquires a magnitudewhich is intermediate the voltage between the line 33 and the negativeline 52, in view of the base current flowing through the resistor 73 ofthe OR stage 75. The charging transistor 61, consequently,can deliver aconstant charging current for the storage capacitor 60. Within theduration of the pulse J,,, the voltage U, rises across the capacitor60in a linear manner, as shown in FIG. 2. This linearizing votlage takesplace from the instant of time t, to the terminal instant 2 of the pulse1,. However, as soon as the end of this pulse is reached and theinverting transistor 70 becomes again conducting, the collector of thistransistor receives a substantially large negative potential, as doesalso the collector of the charging transistor 61. As a result, thecharge accumulated in the meantime on the capacitor 60 causes the baseof the switching transistor 63 to be also strongly negative, so that thetransistor 63 becomes turned off until the charge disappears through thedischarge transistor 62. v

Under the conditions determined by FIG. 2, the discharge process takesplace from the instant of time until the instant t During this timeinterval the switching transistor 63 is again conducting. Since the ORtransistor 75 can be held turned on through the second coupling resistor78 and the collector resistor 68 while the switching transistor 63 isturned off, an extended pulse .1, becomes joined to the pulse J,,. Thesetwo pulses together form a pulse J, which determines the openingduration of the fuel injection valves, and therefore the quantity offuel injected.

As shown in the lower parts of FIG. 2, the discharge of storagecapacitor 60 occurs during the interval of the extended pulse 1,, in amanner which is not constant, and the discharge takes place through thetransistor 62. The correcting or compensation circuit 30 provides thatfor the entireengine speed range as well as load range, the extendedpulse is compensated or corrected so that it remains constant. Inparticular, the compensation arrangement 30 has a monostable stage whichhas a constant time interval of approximately 1 millisecond. Themonostable stage consists of a transistor 85 which is of the npn typeand has its base connected to the negative supply line 52, through aresistor 86. The base of this transistor is also connected to thecathode of a diode 87, while the anode of this diode leads to thepositive supply line 33 through a resistor 88. This resistor 88maintains the transistor 85 conducting during its initial or inoperativestate. In order that the transistor is switched to its unstable,nonconducting state through the pulse 1,, provided by the multivibrator25, the base of transistor 85 leads to the collector of the, inputtransistor 31 of the multivibrator 35, through a resistor 89 andcapacitor 90. The time constant of this series RC circuit isapproximately 1 millisecond. A voltagedivider is, furthermore, providedwithin the circuit 30. This voltage divider forming part of anadjustment means consists of fixed resistors 91 and 92, and apotentiometer 93 between them.

The movable contact 94 of the potentiometer is connected to the anodesof two diodes 96 and 97, through a resistor 95 which serves as alimiting resistor. The diode 96leads to the positive supply line 33through a resistor 98, and to the collector of transistor 85. Thecathode of the-other diode 97 is connected to the emitter of thedischarge transistor 62 of the pulse-extension stage 27. During thecorrecting or compensation interval T, which adjoins directly the timeinstant t the switching transistor 85 is turned off. Since the diode 96is then also non-conducting, auxiliary current can be applied to thecollector of transistor 62, through the diode 97. This transistor 62provides an essentially larger discharge current from the capacitor 60during the time interval T,. The discharge current of the capacitor 60determines substantiallythe duration T, of the stretched or extendedpulse of the stage 27. Since the auxiliary current flows only for lmillisecond as a result of the time interval T, determined by thecapacitor 90, the injection duration can be varied only by the amountattained during theduration T The broken line in FIG.12 represents thefunction of the capacitor voltage U across the storage capacitor 60.This capacitor voltage is determined by the position of the movablecontact 94 of the potentiometer 93 when it is substantially near thenegative potential. In this case, an extension of the injection durationoccurs. The dash-dot line c is applicable, when the movable contact 94of the potentiometer is near the positive potential, whereby ashortening of the injection duration can be achieved. The solid line bin FIG. 2 is applicable for the center position of the contact 94, atwhich time the compensating or correcting arrangement 30 is ineffective.

The particular advantage of the compensating or correcting arrangementdescribed above resides in the condition that the correction orcompensation is independent of the operating conditions as, for example,speed, manifold pressure, etc. Thus, the fuel injection duration isindependent of these operating conditions. IN a simple manner, theinfluence of the additional equipment, for example the manifold pressuresensor becomes compensated through the present invention. The pressuresensor 39 can be considered as representing numerous other elementswhich can be compensated against their manufacturing tolerances throughthe correcting arrangement 30, and as a result the fuelinjectionarrangement can be compensated through installation of the presentinvention, in an electrical manner.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can be applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended 1. In a fuel-injection system for an internalcombustion engine of the type including at least one electricallycontrolled fuel-injection valve having an electrical input, anarrangement for generating electrical valveopening pulses, comprising incombination triggering means for generating triggering signalssynchronized with engine rotation; monostable means having an inputconnected to said triggering means and having an output connected tosaid electrical input of said valve, and operating upon receipt of atriggering signal for generating a first valve-opening pulse having aduration dependent upon at least one variable engine operatingcondition; and pulse-extending means having an input connected to saidmonstable means and having an output connected to said electrical inputof said valve, and operative upon termination of said first pulse forgeneratin'g a second pulse having a duration dependent upon the durationof said first pulse and forming with said first pulse a longer compositevalve-opening pulse, said pulse-extending means including timing meansfor determining the duration of said second pulse, said timing meanscomprising an energy-storing timing component so connected to saidmonostable means as to undergo a first change of stored energy duringsaid first pulse and an opposite second change of stored energy whichcommencesupon termination in said first pulse and whose completionresults in termination of said second pulse,- resistance means connectedto said timing component and having a value causing said second energychange to ordinarily proceed at a first rate, and compensating meansconnected to said pulse-extending means and automatically operativeafter termination of said first pulse and'during an initial portion ofsaid second energy change, for causing said second energy change toproceed during said portion thereof at a different second rate, andthereafter at said first rate upon fixed time period independent of thedurationof said first pulse.

5. An arrangement as defined in claim 1, wherein said timing componentis a timing capacitor, and wherein said compensating means comprisesmeans operative for establishing a flow of current through saidcapacitor during said initial portion of said second energy changesuperimposed upon the component of capacitor current determined by theRC-time-constant of said capacitor and said resistance means.

6. An arrangement as defined in claim 2, wherein said selectingmeanscomprises adjustable voltage divider means so connected to saidpulse-extending means as to be capable of changing said second rate.

7. An arrangement as defined in claim 1, said engine having an airintake passage and a throttle valve 10- cated in said passage, andwherein said engine operating condition is the pressure prevailing insaid passage downstream of said valve.

8. An arrangement as defined in calim 1, wherein said timing componentis a timing capacitor, and wherein said compensating means includes atiming circuit connected to said monostable means and commencingoperation upon termination of said first pulse and comprising aswitching circuit including a switching transistor forinitiatingoperation of said compen' sating means upon termination ofsaid first pulse and for terminating operation of said compensatingmeans in dependence upon operation of said timing circuit, and whereinsaid compensating means further includes adjusting means for changingsaid second rate, said adjusting means comprising an adjustable voltagedivider having a mid-tap, further including a diode having one electrodeconnected to said mid-tap and another electrode connected to said timingcomponent for carrying current between said mid-tap and said timingcomponent, and another diode having one electrode connected to saidmid-tap and another electrode connected to the collector of saidswitching transistor.

18 l III

1. In a fuel-injection system for an internal combustion engine of thetype including at least one electrically controlled fuelinjection valvehaving an electrical input, an arrangement for generating electricalvalve-opening pulses, comprising in combination triggering means forgenerating triggering signals synchronized with engine rotation;monostable means having an input connected to said triggering means andhaving an output connected to said electrical input of said valve, andoperating upon receipt of a triggering signal for generating a firstvalveopening pulse having a duration dependent upon at least onevariable engine operating condition; and pulse-extending means having aninput connected to said monstabLe means and having an output connectedto said electrical input of said valve, and operative upon terminationof said first pulse for generating a second pulse having a durationdependent upon the duration of said first pulse and forming with saidfirst pulse a longer composite valve-opening pulse, said pulse-extendingmeans including timing means for determining the duration of said secondpulse, said timing means comprising an energy-storing timing componentso connected to said monostable means as to undergo a first change ofstored energy during said first pulse and an opposite second change ofstored energy which commences upon termination In said first pulse andwhose completion results in termination of said second pulse, resistancemeans connected to said timing component and having a value causing saidsecond energy change to ordinarily proceed at a first rate, andcompensating means connected to said pulse-extending means andautomatically operative after termination of said first pulse and duringan initial portion of said second energy change, for causing said secondenergy change to proceed during said portion thereof at a differentsecond rate, and thereafter at said first rate upon termination ofoperation of said compensating means.
 2. An arrangement as defined inclaim 1, wherein said compensating means comprises adjusting means forselectably changing said second rate.
 3. An arrangement as defined inclaim 1, wherein said initial portion of said second energy changecommences at the time of termination of said first pulse.
 4. Anarrangement as defined in claim 1, wherein said compensating meansincludes a timing circuit for maintaining said compensating meansoperative for a fixed time period independent of the duration of saidfirst pulse.
 5. An arrangement as defined in claim 1, wherein saidtiming component is a timing capacitor, and wherein said compensatingmeans comprises means operative for establishing a flow of currentthrough said capacitor during said initial portion of said second energychange superimposed upon the component of capacitor current determinedby the RC-time-constant of said capacitor and said resistance means. 6.An arrangement as defined in claim 2, wherein said selecting meanscomprises adjustable voltage divider means so connected to saidpulse-extending means as to be capable of changing said second rate. 7.An arrangement as defined in claim 1, said engine having an air intakepassage and a throttle valve located in said passage, and wherein saidengine operating condition is the pressure prevailing in said passagedownstream of said valve.
 8. An arrangement as defined in calim 1,wherein said timing component is a timing capacitor, and wherein saidcompensating means includes a timing circuit connected to saidmonostable means and commencing operation upon termination of said firstpulse and comprising a switching circuit including a switchingtransistor for initiating operation of said compensating means upontermination of said first pulse and for terminating operation of saidcompensating means in dependence upon operation of said timing circuit,and wherein said compensating means further includes adjusting means forchanging said second rate, said adjusting means comprising an adjustablevoltage divider having a mid-tap, further including a diode having oneelectrode connected to said mid-tap and another electrode connected tosaid timing component for carrying current between said mid-tap and saidtiming component, and another diode having one electrode connected tosaid mid-tap and another electrode connected to the collector of saidswitching transistor.